Culture-expanded T suppressor cells and methods of use thereof

ABSTRACT

This invention relates to culture-expanded T suppressor cells derived from CD25-CD4+ T cells, and their use in modulating immune responses. This invention provides methods of producing culture-expanded T suppressor cells, which are antigen specific, and their use in modulating autoimmune diseases and transplantation rejection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/074,925, filed Mar. 9, 2005 now abandoned, which claims thebenefit of U.S. Provisional Application Ser. No. 60/551,354, filed Mar.10, 2004, which is hereby incorporated by reference in its entirety.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was conducted with U.S. Government support under NationalInstitutes of Health grant Number NIH 5 P01 AI 51573. The government hascertain rights in the invention.

FIELD OF THE INVENTION

This invention relates to culture-expanded T suppressor cells and theiruse in modulating immune responses. This invention provides facilemethods of producing culture-expanded T suppressor cells from a moreabundant yet quiescent population of naïve T cells, which are antigenspecific, and their use in modulating complex autoimmune diseases.

BACKGROUND OF THE INVENTION

Tolerance mechanisms for autoreactive T cells can be of “intrinsic” and“extrinsic” varieties. Intrinsic mechanisms include deletion and anergyof self-reactive T cells, while extrinsic mechanisms include differentregulatory T cells (Tregs) that suppress other self-reactive T cells.One type of extrinsic suppressor is the CD25⁺ CD4⁺ T cell, whichconstitutes 5-10% of CD4⁺ peripheral T cells. These are produced in thethymus and maintain tolerance to self-antigens, as well as play a rolein other immune responses, such as in infection, transplants and graftversus host disease. In autoimmune diseases such as diabetes,considerable effort has been focused on expanding the small numbers ofsuch Tregs. Expansion of this population using methods such as, forexample, employing dendritic cells presenting antigenic peptide or a Tcell receptor cross-linking agent, are described in U.S. patentapplication Ser. No. 11/074,925, filed Mar. 9, 2005.

However, the CD25⁻ CD4⁺ T cell population is a more abundant populationwith the potential to differentiate into Tregs. While it is known thatthis T cell population can be differentiated into CD4⁺CD25⁺ T regs bystimulation with mitogenic antibodies in the presence of TGF-β1, it isnot known whether these induced cells are functionally identical toTregs that develop in the thymus. Such “induced T regs” with isletspecificity can prevent diabetes in lymphopoietic models, but theirability to induce tolerance at late pathogenic stages of autoimmunity,such as in already-diabetic NOD mice, has not been fully addressed.

In T cell population, the transcription factor, FoxP3, is important forCD25⁺ CD4⁺ T cell suppressor activity, and children who are born withdefective FoxP3 rapidly develop autoimmunity, such as, for example,autoimmune diabetes. Models for the study of autoimmunity have played acritical role in both the understanding of the pathogenesis, and thedevising of therapeutic strategies for these diseases. In a mouse modelof autoimmune diabetes, the non-obese diabetic (NOD) mice, for example,CD25⁺ CD4⁺ regulatory T cells inhibit diabetes development, making thisextrinsic tolerance mechanism an attractive target to developantigen-specific therapies for autoimmune disease. In an experimentalmodel of multiple sclerosis mediated by transgenic T cells specific tomyelin basic protein, CD25⁺ CD4⁺ T cells specific for this antigenshowed better suppression of disease than CD25⁺ CD4⁺ T cells with T cellreceptors (TCRs) specific for other antigens. These findings suggest arole for antigen-specific CD25⁺ CD4⁺ T cells in suppressingautoimmunity.

Means for expanding CD25⁺ CD4⁺ T cells without the use of mitogenicstimuli to differentiate T regs has numerous potential therapeuticadvantages.

SUMMARY OF THE INVENTION

In one embodiment, an isolated, culture-expanded CD25⁺CD4⁺ T suppressorcell population is provided, wherein said population is prepared by theprocess of exposing CD25⁻CD4⁺ T cells to dendritic cells, antigen andTGF-β1. In another embodiment the CD25⁻CD4⁺ T cells are Foxp3−. Inanother embodiment, the dendritic cells are presenting the antigen or apeptide thereof. In yet another embodiment, the CD25⁺CD4⁺ populationfurther expresses Foxp3 on its surface. In a further embodiment, theCD25⁺CD4⁺ population is antigen specific. In yet a further embodiment,the antigen is a self-antigen, or a derivative thereof, such as but nolimited to a self antigen is expressed on pancreatic beta cells, or atransplantation antigen.

In another embodiment, a method is provided for producing an isolated,culture-expanded CD25⁺CD4⁺ T suppressor cell population, comprising thesteps of (a) contacting a population of CD25⁻CD4⁺ T cells with dendriticcells; an antigen selected from the group consisting of an antigenicpeptide, an antigenic protein, and a derivative thereof; and TGF-β1, fora period of time resulting in antigen-specific CD25⁺CD4⁺ T celldifferentiation and expansion; and (b) isolating the expanded CD25⁺CD4⁺T cells obtained in (a). In another embodiment, the dendritic cells arepresenting the antigen or a peptide thereof. In yet another embodiment,the CD25⁺CD4⁺ population further expresses Foxp3 on its surface. In afurther embodiment, the CD25⁺CD4⁺ population is antigen specific. In yeta further embodiment, the antigen is a self-antigen, or a derivativethereof, such as but no limited to a self antigen is expressed onpancreatic beta cells, or a transplantation antigen.

In still another embodiment, a method is provided for delaying onset,reducing incidence, suppressing or treating autoimmunity, an autoimmunedisease or an autoimmune disorder in a subject, comprising the steps of(a) contacting a population of CD25⁻CD4⁺ T cells with dendritic cells;an antigen selected from the group consisting of an antigenic peptide,an antigenic protein, and a derivative thereof; and TGF-β1, for a periodof time resulting in antigen-specific CD25⁺CD4⁺ T cell differentiationand expansion; and (b) administering the expanded CD25⁺CD4⁺ T cellsobtained in (a) to a subject. The dendritic cells, in one embodiment,are presenting the antigen or a peptide thereof. In another embodiment,the dendritic cells are isolated from said subject. In anotherembodiment, the CD25⁻CD4⁺ T cells are isolated from said subject. Inanother embodiment, the T cells are syngeneic or allogeneic, withrespect to said dendritic cells and said subject. The CD25⁺CD4⁺ Tsuppressor cell population, in another embodiment, further expressesFoxp3 on its surface. In another embodiment, the CD25⁺CD4⁺ T suppressorcell population is antigen specific.

In other embodiments, the antigen is a self-antigen, or a derivativethereof, such as but not limited to a self antigen is expressed onpancreatic beta cells, or a transplantation antigen. In still otherembodiment, the expanded CD25⁺CD4⁺ T suppressor cell populationsuppresses an autoimmune response, such as against rheumatoid arthritisor against an inflammatory response, an allergic response, ordownmodulates an immune response. The immune response can be, in otherembodiment, graft versus host disease or host versus graft disease. Instill other embodiments, the dendritic cells are isolated from a subjectsuffering from an autoimmune disease or disorder, such as an individualwith a allergic response, a recipient of a transplant, or the antigenicpeptide or antigenic protein or derivative thereof is associated withsaid autoimmune disease or disorder. In one embodiment, the autoimmunedisease or disorder is type I diabetes. In another embodiment, theantigenic peptide or protein is expressed in pancreatic beta cells. Inanother embodiment, the antigenic peptide is a BDC mimetope.

In another embodiment, a method is provided for downmodulating an immuneresponse in a subject, comprising the steps of (a) contacting apopulation of CD25⁻CD4⁺ T cells with dendritic cells; an antigenselected from the group consisting of an antigenic peptide, an antigenicprotein, and a derivative thereof; and TGF-β1, for a period of timeresulting in antigen-specific CD25⁺CD4⁺ T cell differentiation andexpansion; and (b) administering the expanded CD25⁺CD4⁺ T cells obtainedin (a) to a subject. The dendritic cells, in one embodiment, arepresenting the antigen or a peptide thereof. In another embodiment, thedendritic cells are isolated from said subject. In another embodiment,the CD25⁻CD4⁺ T cells are isolated from said subject. In anotherembodiment, the T cells are syngeneic or allogeneic, with respect tosaid dendritic cells and said subject. The CD25⁺CD4⁺ T suppressor cellpopulation, in another embodiment, further expresses Foxp3 on itssurface. In another embodiment, the CD25⁺CD4⁺ T suppressor cellpopulation is antigen specific.

In other embodiments, the antigen is a self-antigen, or a derivativethereof, such as but not limited to a self antigen is expressed onpancreatic beta cells, or a transplantation antigen. In still otherembodiment, the expanded CD25⁺CD4⁺ T suppressor cell populationsuppresses an autoimmune response, such as against rheumatoid arthritisor against an inflammatory response, an allergic response, ordownmodulates an immune response. The immune response can be, in otherembodiment, graft versus host disease or host versus graft disease. Instill other embodiments, the dendritic cells are isolated from a subjectsuffering from an autoimmune disease or disorder, such as an individualwith a allergic response, a recipient of a transplant, or the antigenicpeptide or antigenic protein or derivative thereof is associated withsaid autoimmune disease or disorder. In one embodiment, the autoimmunedisease or disorder is type I diabetes. In another embodiment, theantigenic peptide or protein is expressed in pancreatic beta cells. Inanother embodiment, the antigenic peptide is a BDC mimetope.

In another embodiment, a method is provided for delaying onset, reducingincidence, suppressing or treating autoimmunity, an autoimmune diseaseor autoimmune disorder in a subject, comprising the step of contacting adendritic cell population in vivo with an antigenic peptide or proteinassociated with an autoimmune response in said subject, or a derivativethereof, and TGF-β1 for a period of time whereby said dendritic cellscontact CD25⁻CD4⁺ T cells in said subject, inducing and stimulatingantigen-specific induction and expansion into CD25⁺CD4⁺ T cells in saidsubject, wherein expanded CD25⁺CD4⁺ T cells suppress an autoimmuneresponse in said subject, thereby delaying onset, reducing incidence,suppressing or treating autoimmunity, an autoimmune disease or anautoimmune disorder.

In the aspects of the invention mentioned above, in one embodiment thedendritic cells can be modified to express the aforementioned antigen.In other embodiments, the dendritic cells can be modified or treated toexpress TGF-β1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows that splenic dendritic cells (DCs) efficiently induce Foxp3expression from naïve CD4⁺CD25⁻ T cells. (A) Cell surface expression ofCD40, CD86, and MHC class II (I-A^(g7)) of freshly isolated NOD splenicCD11c⁺ DCs. (B) Foxp3 expression by precultured sorted CD4⁺CD25⁻ CD62L⁺BDC2.5 T cells and induction in T cells after culture with or without 2ng/ml TGF-β1 on day 6 of culture. Expression of CD62L by preculturedCD4⁺CD25⁻ BDC2.5 T cells is also shown. (C) Time-course of induction ofCD4⁺CD25⁺Foxp3⁺ BDC2.5 T cells from naïve CD4⁺CD25⁻Foxp3⁻ BDC2.5 T cellsin the presence of 2 ng/ml TGF-β1. (Upper) Total number of Foxp3⁺ Tcells per well. (Lower) Percentages of Foxp3⁺ T cells determined byintracellular staining on days 2, 3, 4, 5, 6, and 10 of DC-T cultures.The isotype control for day 3 is shown. (D) Quantification of Foxp3 mRNAby real-time RT-PCR. Samples were prepared from enriched CD25⁺ fractionsof the resulting T cells from cocultures with or without 2 ng/ml TGF-β1or freshly isolated CD4⁺CD25⁺ and CD4⁺CD25⁻ BDC2.5 T cells. Values werestandardized by 18s RNA and expressed as fold of increase compared withprecultured freshly isolated CD4⁺CD25⁻ cells. (E) Dose-response ofTGF-β1 determined on day 6 of DC-T cocultures at indicatedconcentrations of TGF-β1. The isotype control for the 0.01 ng/ml dose isshown. All results are representative of two to four separateexperiments.

FIG. 2 shows the characterization of CD4⁺CD25⁺Foxp3⁺ BDC T cells inducedby DCs and TGF-β1. (A) Intracellular expressions of IFN-γ, IL-10, andIL-17 on day 6 of DC-T coculture. The addition of 20 ng/ml IL-6 inducedL-17 expression. (B) Expression of CD62L, CTLA-4, and GITR on day 6 ofDC-T coculture. Cells cultured in the absence of TGF-β1 were also shownfor comparison. Shaded histogram, isotype control; solid line, +TGF-β1;dotted line, −TGF-β1. (C) BDC clonotype expression. (Left) Freshlyisolated BDC2.5 CD4⁺ T cells. (Right) T cells on day 6 after culture.Shaded histogram, isotype control; thick line, T cells cultured with DCsand TGF-β1; thin line, T cells cultured with anti-CD3, anti-CD28, andTGF-β1. All results are representative of two to four separateexperiments.

FIG. 3 shows that CD4⁺CD25⁺Foxp3⁺ BDC T cells induced by DCs and TGF-β1suppress BDC-specific T cell proliferation and cytokine production.After 6 days of culture with (A) or without (B) TGF-β1, CD11c⁺ cellswere depleted and CD25⁺ cells were enriched. FACS plots constructedafter the enrichment are shown (Left). Proliferation assays were set upwith CD4⁺CD25⁻ cells from BDC2.5 mice [responders (R)], APCs from NODmice, and BDC peptide (100 ng/ml). Increasing numbers of the inducedCD4⁺CD25⁺ cells [suppressors (S)] were added at ratios indicated.Proliferation was assessed by [³H]thymidine uptake (Center), and IFN-γwas measured from culture supernatants (Right) as described in Materialsand Methods.

FIG. 4 shows that CD4⁺CD25⁺Foxp3⁺ BDC T cells induced by DCs and TGF-β1block the development of diabetes in NOD.scid recipients. NOD.scid micewere injected i.v. with 10⁷ spleen cells from diabetic NOD females witheither nothing (red triangles) or the indicated numbers of CD4⁺CD25⁺ BDCT cells from cultures with splenic DCs in the presence (+TGF-β1 BDC T,open circles) or absence (−TGF-β1 BDC T, solid squares) of TGF-β1.P<0.0001, control vs. 3×10⁵+TGF-β1 BDC T cells; P<0.0001, control vs.3×10⁴+TGF-β1 BDC T cells.

FIG. 5 shows that CD4⁺CD25⁺Foxp3⁺ BDC T cells induced by DCs and TGF-β1protect syngeneic islet grafts from ongoing autoimmune destruction inspontaneously diabetic NOD recipients. A total of 500 NOD islets weretransplanted into kidney subcapsular space either alone or with3×10⁵+TGF-β1 BDC T cells or −TGF-β1 BDC T cells. Day 0 indicates the dayof islet transplantation. Data shown is the summary of graft survivalafter transplantation for individual mice. P<0.0001 for comparison ofgraft survival among all three groups; P=0.0069, −TGF-β1 BDC T vs.islets only; P=0.0001, +TGF-β1 BDC T vs. islets only. Data represent thecombination of three separate transplant experiments with cells fromthree separate cultures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Naive CD4⁺CD25⁻ T cells comprise an abundant and population of potentialT reg cells (suppressor T cells). If induced and expanded in vitro, exvivo or in vivo under the proper conditions or with the propertreatments, this population represents a significantly prevalent andpractical source of potential antigen-specific suppressors clinicallyuseful for addressing immune-mediated diseases including autoimmunediseases such as diabetes, as well as induction of tolerance in, forexample, transplantation immunity.

Thus, in one embodiment, induction and differentiation of CD4⁺CD25⁻ Tcells into T suppressor cells is achieved by exposure of naive CD4⁺CD25⁻T cells to dendritic cells pulsed with or exposed at least todisease-specific antigen or peptide, in the presence of TGF-β1. Inanother embodiment, the disease specific antigen is an autoimmunedisease antigen. In another embodiment, the disease specific antigen isa transplant antigen. In another embodiment, the method is carried outin vitro. In still another embodiment, the method is carried out exvivo. In yet another embodiment, the method is carried out in vivo.

As will be described in greater detail below, in other embodiments, aculture-expanded population of CD25⁺CD4⁺ T suppressor cells is providedby carrying out the aforementioned methods. In another embodiment, thepopulation is used for suppressing or downregulating an immune responseor treating an autoimmune disease or disorder in a subject. Such methodsin one embodiment can be carried out ex vivo. In yet other embodiments,the induction and expansion of the aforementioned population can beachieved in vivo.

As will be seen in the Examples below, the ability of dendritic cells(DCs) from NOD mice to induce islet antigen-specific CD4⁺CD25⁺Foxp3⁺ Tcells from naive CD4⁺CD25⁻Foxp3⁻ T cells was demonstrated. By using Tcells from BDC2.5 mice, a well described diabetogenic CD4⁺ TCRtransgenic system, DCs, together with specific peptide and TGF-β1,induced CD4⁺CD25⁺Foxp3⁺ T cells that maintain islet-antigen specificity.The stimulation with DCs and TGF-β1 results in T cells that have highlevels of Foxp3 as well as specific TCR expression, and these T cellsare able to suppress proliferation and cytokine responses in vitro.Importantly, the DC+ TGF-β1-induced CD4⁺CD25⁺Foxp3⁺ T cells also arepotent suppressors of ongoing autoimmune diabetes in vivo and providesignificant protection for syngeneic islet grafts in diabetic mice fromestablished autoimmune destruction.

The generation of T suppressor cells and various methods of inventionare applicable generally to the suppression of the immune response andtreatment of autoimmune diseases and disorders. The methods are notlimited to any particular antigen, disease, or expression of cellsurface markers on CD25⁺CD4⁺ T suppressor cells induced and expanded byfollowing the teachings herein. By selection of at least one antigen orprotein for which suppression is desired, by following the teachingherein, a useful population of T suppressor cells is generated in vitro,ex vivo or in vivo.

Thus, in one embodiment is provided an isolated culture-expanded Tsuppressor cell population, which expresses CD25 and CD4 on its cellsurface, methods of producing the same, and methods of use thereof,wherein the CD25⁺ CD4⁺ T cells are produced by the process of exposingCD4⁺CD25⁻ cells to dendritic cells, antigen and TGF-β1. In anotherembodiment, the process comprises exposing CD4⁺CD25⁻ cells to dendriticcells presenting antigen, and TGF-β1. As will be described in moredetail below, in certain embodiments the dendritic cells can be modifiedto express antigen, and in other embodiments, to express or be inducedto express TGF-β1.

In one embodiment, the phrase “T suppressor cell” or “suppressor Tcell”, or “regulatory T cell”, refers to a T cell population thatinhibits or prevents the activation, or in another embodiment, theeffector function, of another T lymphocyte. In one embodiment, the Tsuppressors are a homogenous population, or in another embodiment, aheterogeneous population.

The T suppressor cells induced by the processes of this inventionexpress CD25 and CD4 on their cell surface. In another embodiment, the Tsuppressor cells may express Foxp3. In another embodiment, the Tsuppressor cells may express CTLA-4, or in another embodiment, GITR. Inone embodiment, the T suppressor cells may be classified asCTLA-4^(high) expressors, or in another embodiment, the T suppressorcells may be classified as GITR^(high), or in another embodiment, acombination thereof. In another embodiment, the T suppressor cells ofthis invention are CD69⁻. In another embodiment, the T suppressor cellsof this invention are CD62L^(hi), CD45RB^(lo), CD45RO^(hi), CD45RA⁻,α_(E)β₇ integrin expressors, or any combination thereof. It is to beunderstood that the isolated culture-expanded T suppressor cells of thisinvention may express in addition to CD25 and CD4 any number orcombination of cell surface markers, as described herein, and as is wellknown in the art, and are to be considered as part of this invention.

In one embodiment, the T suppressor cells of this invention express theCD62L antigen, which in one embodiment, is a 74 kDa glycoprotein, and inanother embodiment, is a member of the selectin family of cell surfacemolecules. In another embodiment, the phrase “CD62L” may also bereferred to as “L-selectin”, “LECAM-1”, or “LAM-1”, all of which are tobe considered synonymous herein. CD62L binds a series of glycoproteins,in other embodiments, including CD34, GlyCAM-1 and MAdCAM-1. CD62L isimportant, in another embodiment, for homing of the lymphocytes via thehigh endothelial venules to peripheral lymph nodes and Peyer's patches,where in another embodiment, they may carry out their effector function,for example, and in one embodiment, suppression of autoimmune responses.The CD62L antigen also contributes, in another embodiment, to therecruitment of leukocytes from the blood to areas of inflammation, andin another embodiment, recruited cells may thereby be induced to becomesuppressor cells.

In one embodiment, the T suppressor cells of this invention are obtainedby positive selection for expression of CD4 and CD25, and in anotherembodiment, the T suppressor cells may also be selected for the absenceof CD45RA expression, i.e. negative selection procedures, as are wellknown in the art. In another embodiment, other markers can be used tofurther separate subpopulations of the T suppressor cells, includingCD69, CCR6, CD30, CTLA-4, CD62L, CD45RB, CD45RO, Foxp3, or a combinationthereof.

In one embodiment, the naïve CD25⁻CD4⁺ T cells of this invention may beobtained from in vivo sources, such as, for example, peripheral blood,leukopheresis blood product, apheresis blood product, peripheral lymphnodes, gut associated lymphoid tissue, spleen, thymus, cord blood,mesenteric lymph nodes, liver, sites of immunologic lesions, e.g.synovial fluid, pancreas, cerebrospinal fluid, tumor samples,granulomatous tissue, or any other source where such cells may beobtained. In one embodiment, the T cells are obtained from humansources, which may be, in another embodiment, from human fetal,neonatal, child, or adult sources. In another embodiment, the T cells ofthis invention may be obtained from animal sources, such as, forexample, porcine or simian, or any other animal of interest. In anotherembodiment, the T cells of this invention may be obtained from subjectsthat are normal, or in another embodiment, diseased, or in anotherembodiment, susceptible to a disease of interest.

In one embodiment, the T cells and/or dendritic cells, as describedfurther hereinbelow, of this invention are isolated from tissue, and, inanother embodiment, an appropriate solution may be used for dispersionor suspension, toward this end. In another embodiment, T cells and/ordendritic cells, as described further hereinbelow, of this invention maybe cultured in solution.

Such a solution may be, in another embodiment, a balanced salt solution,such as normal saline, PBS, or Hank's balanced salt solution, or others,each of which represents another embodiment of this invention. Thesolution may be supplemented, in other embodiments, with fetal calfserum, bovine serum albumin (BSA), normal goat serum, or other naturallyoccurring factors, and, in another embodiment, may be supplied inconjunction with an acceptable buffer. The buffer may be, in otherembodiments, HEPES, phosphate buffers, lactate buffers, or the like, aswill be known to one skilled in the art.

In another embodiment, the solution in which the T cells or dendriticcells of this invention may be induced, differentiated or expanded is inmedium is which is serum-free, which may be, in another embodiment,commercially available, such as, for example, animal protein-free basemedia such as X-VIVO 10™ or X-VIVO 15™ (BioWhittaker, Walkersville,Md.), Hematopoietic Stem Cell-SFM media (GibcoBRL, Grand Island, N.Y.)or any formulation which promotes or sustains cell viability. Serum-freemedia used, may, in another embodiment, be as those described in thefollowing patent documents: WO 95/00632; U.S. Pat. No. 5,405,772; PCTUS94/09622. The serum-free base medium may, in another embodiment,contain clinical grade bovine serum albumin, which may be, in anotherembodiment, at a concentration of about 0.5-5%, or, in anotherembodiment, about 1.0% (w/v). Clinical grade albumin derived from humanserum, such as Buminate® (Baxter Hyland, Glendale, Calif.), may be used,in another embodiment.

In another embodiment, the CD25⁻CD4 T cells of this invention may beisolated or separated via affinity-based separation methods. Techniquesfor affinity separation may include, in other embodiments, magneticseparation, using antibody-coated magnetic beads, affinitychromatography, cytotoxic agents joined to a monoclonal antibody or usein conjunction with a monoclonal antibody, for example, complement andcytotoxins, and “panning” with an antibody attached to a solid matrix,such as a plate, or any other convenient technique. In other embodiment,separation techniques may also include the use of fluorescence activatedcell sorters, which can have varying degrees of sophistication, such asmultiple color channels, low angle and obtuse light scattering detectingchannels, impedance channels, etc. It is to be understood that anytechnique, which enables separation of the T cells of this invention maybe employed, and is to be considered as part of this invention.

In another embodiment, the affinity reagents employed in the separationmethods may be specific receptors or ligands for the cell surfacemolecules indicated hereinabove. In other embodiments, peptide-MHCantigen and T cell receptor pairs may be used; peptide ligands andreceptor; effector and receptor molecules, or others. Antibodies and Tcell receptors may be monoclonal or polyclonal, and may be produced bytransgenic animals, immunized animals, immortalized human or animalB-cells, cells transfected with DNA vectors encoding the antibody or Tcell receptor, etc. The details of the preparation of antibodies andtheir suitability for use as specific binding members are well-known tothose skilled in the art.

In another embodiment, the antibodies utilized herein may be conjugatedto a label, which may, in another embodiment, be used for separation.Labels may include, in other embodiments, magnetic beads, which allowfor direct separation, biotin, which may be removed with avidin orstreptavidin bound to, for example, a support, fluorochromes, which maybe used with a fluorescence activated cell sorter, or the like, to allowfor ease of separation, and others, as is well known in the art.Fluorochromes may include, in one embodiment, phycobiliproteins, suchas, for example, phycoerythrin, allophycocyanins, fluorescein, Texasred, or combinations thereof. In one embodiment, antibodies are labeled.In one embodiment suppressors can be purified by positive or negativeselection.

In one embodiment, cell separations utilizing antibodies will entail theaddition of an antibody to a suspension of cells, for a period of timesufficient to bind the available cell surface antigens. The incubationmay be for a varied period of time, such as in one embodiment, for 5minutes, or in another embodiment, 15 minutes, or in another embodiment,30 minutes. Any length of time which results in specific labeling withthe antibody, with minimal non-specific binding is to be consideredenvisioned for this aspect of the invention.

In another embodiment, the staining intensity of the cells can bemonitored by flow cytometry, where lasers detect the quantitative levelsof fluorochrome (which is proportional to the amount of cell surfaceantigen bound by the antibodies). Flow cytometry, or FACS, can also beused, in another embodiment, to separate cell populations based on theintensity of antibody staining, as well as other parameters such as cellsize and light scatter.

In another embodiment, the labeled cells are separated based on theirexpression of CD4 and CD25. In another embodiment, the cells may befurther separated based on their expression of Foxp3. The separatedcells may be collected in any appropriate medium that maintains cellviability, and may, in another embodiment, comprise a cushion of serumat the bottom of the collection tube.

In another embodiment, the culture containing the induced,differentiated or expanded T cells of this invention may containcytokines or growth factors to which the cells are responsive. In oneembodiment, the cytokines or growth factors promote survival, growth,function, or a combination thereof of the T suppressor cells. Cytokinesand growth factors may include, in other embodiment, polypeptides andnon-polypeptide factors. In one embodiment, the cytokines may compriseinterleukins.

In one embodiment, the isolated culture-expanded T suppressor cellpopulations of this invention are antigen specific.

In one embodiment, the term “antigen specific” refers to a property ofthe population such that supply of a particular antigen, or in anotherembodiment, a fragment of the antigen, results, in one embodiment, inspecific suppressor cell proliferation, when presented the antigen, inthe context of MHC. In another embodiment, supply of the antigen orfragment thereof, results in suppressor cell production of interleukin2, or in another embodiment, enhanced expression of the T cell receptor(TCR) on its surface, or in another embodiment, suppressor cellfunction. In one embodiment, the T suppressor cell population expressesa monoclonal T cell receptor. In another embodiment, the T suppressorcell population expresses polyclonal T cell receptors.

In one embodiment, the T suppressor cells will be of one or morespecificities, and may include, in another embodiment, those thatrecognize a mixture of antigens derived from an antigenic source, suchas, for example, in diabetes, where recognition of a pancreatic betacell line or islet tissue itself may be used to expand the T suppressorcells. In one embodiment suppressors can be purified by positive ornegative selection.

In another embodiment, the antigen is a self-antigen. In one embodiment,the term “self-antigen” refers to an antigen that is normally expressedin the body from which the suppressor T cell population is derived. Inanother embodiment, self-antigen is comparable to one, or, in anotherembodiment, indistinct from one normally expressed in a body from whichthe suppressor T cell population is derived, though may not directlycorrespond to the antigen. In another embodiment, self-antigen refers toan antigen, which when expressed in a body, may result in the educationof self-reactive T cells. In one embodiment, self-antigen is expressedin an organ that is the target of an autoimmune disease. In oneembodiment, the self-antigen is expressed in a pancreas, thyroid,connective tissue, kidney, lung, digestive system or nervous system. Inanother embodiment, self-antigen is expressed on pancreatic beta cells.

In another embodiment, a library of peptides that span an antigenicprotein is used in this invention. In one embodiment, the peptides areabout 15 amino acids in length, and may, in another embodiment, bestaggered every 4 amino acids along the length of the antigenic protein.

In one embodiment, the isolated culture-expanded T suppressor cellpopulation prepared by the process described herein suppresses anautoimmune response. In one embodiment, the term “autoimmune response”refers to an immune response directed against an auto- or self-antigen.In one embodiment, the autoimmune response is directed to ameliorationof rheumatoid arthritis, multiple sclerosis, diabetes mellitus,myasthenia gravis, pernicious anemia, Addison's disease, lupuserythematosus, Reiter's syndrome, atopic dermatitis, psoriasis or Gravesdisease. In one embodiment, the autoimmune disease caused in the subjectis a result of self-reactive T cells, which recognize multipleself-antigens. In one embodiment, the T suppressor cell populations ofthis invention may be specific for a single self-antigen in a diseasewhere multiple self-antigens are recognized, yet the T suppressor cellpopulation effectively suppresses the autoimmune disease. Such aphenomenon was exemplified herein, for example, in FIG. 4, where betacell peptide-pulsed DC and TGF-β1-induced CD25⁺ CD4⁺ suppressor T cellsinto NOD mice rendered diabetic with diabetic spleen cells, preventedthe development of diabetes, which is a disease wherein auto-reactive Tcells recognize multiple self-antigens. Furthermore, islet grafts wereprotected from autoimmune destruction (FIG. 5).

In another embodiment, the antigen may be any molecule recognized by theimmune system of the mammal as foreign. For example, the antigen may beany foreign molecule, such as a protein (including a modified proteinsuch as a glycoprotein, a mucoprotein, etc.), a nucleic acid, acarbohydrate, a proteoglycan, a lipid, a mucin molecule, or othersimilar molecule, including any combination thereof. The antigen may, inanother embodiment, be a cell or a part thereof, for example, a cellsurface molecule. In another embodiment, the antigen may derive from aninfectious virus, bacterium, fungus, or other organism (e.g., protists),or part thereof. These infectious organisms may be active, in oneembodiment or inactive, in another embodiment, which may beaccomplished, for example, through exposure to heat or removal of atleast one protein or gene required for replication of the organism.

In one embodiment, the term “antigen” refers to a protein, or peptide,associated with a particular disease for which the cells of thisinvention are being used to modulate, or for use in any of the methodsof this invention. In one embodiment, the term “antigen” may refer to asynthetically derived molecule, or a naturally derived molecule, whichshares sequence homology with an antigen of interest, or structuralhomology with an antigen of interest, or a combination thereof. In oneembodiment, the antigen may be a mimetope.

In another embodiment, isolated culture-expanded T suppressor cellpopulation suppresses an inflammatory response. In one embodiment, theterm “inflammatory disorder” refers to any disorder that is, in oneembodiment, caused by an “inflammatory response” also referred to, inanother embodiment, as “inflammation” or, in another embodiment, whosesymptoms include inflammation. By way of example, an inflammatorydisorder caused by inflammation may be a septic shock, and aninflammatory disorder whose symptoms include inflammation may berheumatoid arthritis. The inflammatory disorders of the presentinvention comprise, in another embodiment, cardiovascular disease,rheumatoid arthritis, multiple sclerosis, Crohn's disease, inflammatorybowel disease, systemic lupus erythematosis, polymyositis, septic shock,graft versus host disease, host versus graft disease, asthma, rhinitis,psoriasis, cachexia associated with cancer, or eczema. In oneembodiment, as described hereinabove, the inflammation in the subjectmay be a result of T cells, which recognize multiple antigens in thesubject. In one embodiment, the T suppressor cell populations of thisinvention may be specific for a single antigen where multiple antigensare recognized, yet the T suppressor cell population effectivelysuppresses the inflammation in the subject.

In another embodiment, the isolated culture-expanded T suppressor cellpopulations of this invention suppress an allergic response. In oneembodiment, the term “allergic response” refers to an immune systemattack against a generally harmless, innocuous antigen or allergen.Allergies may in one embodiment include, but are not limited to, hayfever, asthma, atopic eczema as well as allergies to poison oak and ivy,house dust mites, bee pollen, nuts, shellfish, penicillin or othermedications, or any other compound or compounds which induce an allergicresponse. In one embodiment, multiple allergens elicit an allergicresponse, and the antigen recognized by the T suppressor cells of thisinvention may be any antigen thereof.

In another embodiment, the isolated culture-expanded T suppressor cellpopulation downmodulates an immune response. In one embodiment, animmune response to a particular antigen may be beneficial to the host,such as, for example, a response directed against an antigen from apathogen that has invaded the subject. In one embodiment, such an immuneresponse may be too robust, such that even after the pathogen has beeneradicated, or controlled, the immune response is sustained and causesdamage to the host, such as, for example, by causing tissue necrosis, intissue which formerly was infected with the pathogen. In these and othercircumstances, the isolated culture-expanded T suppressor cellpopulation may be useful in downmodulating an immune response, such thatthe host is not compromised in any way by the persistence of such animmune response.

In another embodiment, the immune response, whose downmodulation isdesired is host versus graft disease. With the improvement in theefficiency of surgical techniques for transplanting tissues and organssuch as skin, kidney, liver, heart, lung, pancreas and bone marrow tosubjects, perhaps the principal outstanding problem is the immuneresponse mounted by the recipient to the transplanted allograft ororgan, often resulting in rejection. When allogeneic cells or organs aretransplanted into a host (i.e., the donor and recipient are differentindividual from the same species), the host immune system is likely tomount an immune response to foreign antigens in the transplant(host-versus-graft disease) leading to destruction of the transplantedtissue. Accordingly, the isolated culture-expanded T suppressor cellpopulation may be used, in one embodiment, to prevent such rejection oftransplanted tissue or organ.

In another embodiment, the immune response, whose downmodulation isdesired is graft versus host disease (GVHD). GVHD is a potentially fataldisease that occurs when immunologically competent cells are transferredto an allogeneic recipient. In this situation, the donor'simmunocompetent cells may attack tissues in the recipient. Tissues ofthe skin, gut epithelia and liver are frequent targets and may bedestroyed during the course of GVHD. The disease presents an especiallysevere problem when immune tissue is being transplanted, such as in bonemarrow transplantation; but less severe GVHD has also been reported inother cases as well, including heart and liver transplants. The isolatedculture-expanded T suppressor cell population may be used, in oneembodiment, to preventing or ameliorating such disease.

It is to be understood that the downmodulation of any immune response,via the use of the isolated culture-expanded T suppressor cellpopulations of this invention are to be considered as part of thisinvention, and an embodiment thereof.

In one embodiment, the isolated culture-expanded T suppressor cellpopulations secrete substances, which mediate the suppressive effects.In one embodiment, the T suppressor cells of this invention mediatebystander suppression, without a need for direct cell contact. In oneembodiment, the substances mediating suppression secreted by the Tsuppressor cell populations of this invention may include IL-10, TGF-β1,or a combination thereof. The secretion of TGF-β1 from such cellpopulations can contribute in a paracrine fashion to the furtherinduction and expansion of the T suppressor cell population fromCD25⁻CD4⁺ T cells and induction of Foxp3 expression for the desiredpurposes herein.

In another embodiment, the isolated culture-expanded T suppressor cellpopulations may be engineered to express substances which when secretedmediate suppressive effects, such as, for example, the cytokines listedhereinabove. In another embodiment, the isolated culture-expanded Tsuppressor cell populations may be engineered to express particularadhesion molecules, or other targeting molecules, which, when the cellsare provided to a subject, facilitate targeting of the T suppressor cellpopulations to a site of interest. For example, when T suppressor cellactivity is desired to downmodulate or prevent an immune response at amucosal surface, the isolated culture-expanded T suppressor cellpopulations of this invention may be further engineered to express theα_(e)β₇ adhesion molecule, which has been shown to play a role inmucosal homing. The cells can be engineered to express other targetingmolecules, such as, for example, an antibody specific for a proteinexpressed at a particular site in a tissue, or, in another embodiment,expressed on a particular cell located at a site of interest, etc.Numerous methods are well known in the art for engineering the cells,and may comprise the use of a vector, or naked DNA, wherein a nucleicacid coding for the targeting molecule of interest is introduced via anynumber of methods well described.

A nucleic acid sequence of interest may be subcloned within a particularvector, depending upon the desired method of introduction of thesequence within cells. Once the nucleic acid segment is subcloned into aparticular vector it thereby becomes a recombinant vector.Polynucleotide segments encoding sequences of interest can be ligatedinto commercially available expression vector systems suitable fortransducing/transforming mammalian cells and for directing theexpression of recombinant products within the transduced cells. It willbe appreciated that such commercially available vector systems caneasily be modified via commonly used recombinant techniques in order toreplace, duplicate or mutate existing promoter or enhancer sequencesand/or introduce any additional polynucleotide sequences such as forexample, sequences encoding additional selection markers or sequencesencoding reporter polypeptides. Sequences of interest introduced as anucleic acids such as DNA or RNA include the specific antigens andpolypeptides comprising antigens for which the T regs of the inventionare desiriously directed, as well as the sequence of TGF-β1 whoseexpression by dendritic cells is, in one embodiment, engineered hereby.

There are a number of techniques known in the art for introducing theabove described recombinant vectors into cells, such as, but not limitedto: direct DNA uptake techniques, and virus, plasmid, linear DNA orliposome mediated transduction, receptor-mediated uptake andmagnetoporation methods employing calcium-phosphate mediated andDEAE-dextran mediated methods of introduction, electroporation,liposome-mediated transfection, direct injection, and receptor-mediateduptake (for further detail see, for example, “Methods in Enzymology”Vol. 1-317, Academic Press, Current Protocols in Molecular Biology,Ausubel F. M. et al. (eds.) Greene Publishing Associates, (1989) and inMolecular Cloning: A Laboratory Manual, 2nd Edition, Sambrook et al.Cold Spring Harbor Laboratory Press, (1989), or other standardlaboratory manuals). Bombardment with nucleic acid coated particles isalso envisaged.

The efficacy of a particular expression vector system and method ofintroducing nucleic acid into a cell can be assessed by standardapproaches routinely used in the art. For example, DNA introduced into acell can be detected by a filter hybridization technique (e.g., Southernblotting) and RNA produced by transcription of introduced DNA can bedetected, for example, by Northern blotting, RNase protection or reversetranscriptase-polymerase chain reaction (RT-PCR). The gene product canbe detected by an appropriate assay, for example by immunologicaldetection of a produced protein, such as with a specific antibody, or bya functional assay to detect a functional activity of the gene product,such as an enzymatic assay. If the gene product of interest to beexpressed by a cell is not readily assayable, an expression system canfirst be optimized using a reporter gene linked to the regulatoryelements and vector to be used. The reporter gene encodes a geneproduct, which is easily detectable and, thus, can be used to evaluateefficacy of the system. Standard reporter genes used in the art includegenes encoding β-galactosidase, chloramphenicol acetyl transferase,luciferase and human growth hormone, or any of the marker proteinslisted herein.

In another embodiment, this invention provides a method for producing anisolated, culture-expanded T suppressor cell population, comprisingcontacting CD25⁻ CD4⁺ T cells with dendritic cells and an antigenicpeptide, and TGF-β1, for a period of time resulting in antigen-specificCD25⁺ CD4⁺ T cell expansion and optionally isolating the expanded CD25⁺CD4⁺ T cells thus obtained, thereby producing a culture-expanded,antigen-specific T suppressor cell population.

In one embodiment, the term “dendritic cell” (DC) refers toantigen-presenting cells, which are capable of presenting antigen to Tcells, in the context of MHC. In one embodiment, the dendritic cellsutilized in the methods of this invention may be of any of several DCsubsets, which differentiate from, in one embodiment, lymphoid or, inanother embodiment, myeloid bone marrow progenitors. In one embodiment,DC development may be stimulated via the use of granulocyte-macrophagecolony-stimulating-factor (GM-CSF), or in another embodiment,interleukin (IL)-3, which may, in another embodiment, enhance DCsurvival.

In another embodiment, DCs may be generated from proliferatingprogenitors isolated from bone marrow, as exemplified herein. In anotherembodiment, DCs may be isolated from CD34⁺ progenitors as described byCaux and Banchereau in Nature in 1992, or from monocytes, as describedby Romani et al, J. Exp. Med. 180: 83-93 '94 and Bender et al, J.Immunol. Methods, 196: 121-135, '96 1996. In another embodiment, the DCsare isolated from blood, as described for example, in O'Doherty et al,J. Exp. Med. 178: 1067-1078 1993 and Immunology 82: 487-493 1994, allmethods of which are incorporated fully herewith by reference.

In one embodiment, the DCs utilized in the methods of this invention mayexpress myeloid markers, such as, for example, CD11c or, in anotherembodiment, an IL-3 receptor-α (IL-3Rα) chain (CD123). In anotherembodiment, the DCs may produce type I interferons (IFNs). In oneembodiment, the DCs utilized in the methods of this invention expresscostimulatory molecules. In another embodiment, the DCs utilized in themethods of this invention may express additional adhesion molecules,which may, in one embodiment, serve as additional costimulatorymolecules, or in another embodiment, serve to target the DCs toparticular sites in vivo, when delivered via the methods of thisinvention, as described further hereinbelow.

In one embodiment, the DCs may be obtained from in vivo sources, suchas, for example, most solid tissues in the body, peripheral blood, lymphnodes, gut associated lymphoid tissue, spleen, thymus, skin, sites ofimmunologic lesions, e.g. synovial fluid, pancreas, cerebrospinal fluid,tumor samples, granulomatous tissue, or any other source where suchcells may be obtained. In one embodiment, the dendritic cells areobtained from human sources, which may be, in another embodiment, fromhuman fetal, neonatal, child, or adult sources. In another embodiment,the dendritic cells used in the methods of this invention may beobtained from animal sources, such as, for example, porcine or simian,or any other animal of interest. In another embodiment, dendritic cellsused in the methods of this invention may be obtained from subjects thatare normal, or in another embodiment, diseased, or in anotherembodiment, susceptible to a disease of interest.

Dendritic cell separation may be accomplished in another embodiment, viaany of the separation methods as described herein. In one embodiment,positive and/or negative affinity based selections are conducted. In oneembodiment, positive selection is based on CD86 expression, and negativeselection is based on GRI expression.

In another embodiment, the dendritic cells used in the methods of thisinvention may be generated in vitro by culturing monocytes in presenceof GM-CSF and IL-4.

In one embodiment, the dendritic cells used in the methods of thisinvention may express CD83, an endocytic receptor to increase uptake ofthe autoantigen such as DEC-205/CD205 in one embodiment, or DC-LAMP(CD208) cell surface markers, or, in another embodiment, varying levelsof the antigen presenting MHC class I and II products, or in anotherembodiment, accessory (adhesion and co-stimulatory) molecules includingCD40, CD54, CD58 or CD86, or any combination thereof. In anotherembodiment, the dendritic cells may express varying levels of CD115,CD14, CD68 or CD32.

In one embodiment, mature dendritic cells are used for the methods ofthis invention. In one embodiment, the term “mature dendritic cells”refers to a population of dendritic cells with diminished CD115, CD14,CD68 or CD32 expression, or in another embodiment, a population of cellswith enhanced CD86 expression, or a combination thereof. In anotherembodiment, mature dendritic cells will exhibit increased expression ofone or more of p55, CD83, CD40 or CD86 or a combination thereof. Inanother embodiment, the dendritic cells used in the methods of thisinvention will express the DEC-205 receptor on their surface. In anotherembodiment, maturation of the DCs may be accomplished via, for example,CD40 ligation, CpG oligodeoxyribonucleotide addition, ligation of theIL-1, TNFα or TOLL like receptor ligand, bacterial lipoglycan orpolysaccharide addition or activation of an intracellular pathway suchas TRAF-6 or NF-κB.

In one embodiment, inducing DC maturation may be in combination withendocytic receptor delivery of a preselected antigen. In one embodiment,endocytic receptor delivery of antigen may be via the use of the DEC-205receptor.

In one embodiment, the maturation status of the dendritic may beconfirmed, for example, by detecting either one or more of 1) anincrease expression of one or more of p55, CD83, CD40 or CD86 antigens;2) loss of CD115, CD14, CD32 or CD68 antigen; or 3) reversion to amacrophage phenotype characterized by increased adhesion and loss ofveils following the removal of cytokines which promote maturation ofPBMCs to the immature dendritic cells, by methods well known in the art,such as, for example, immunohistochemistry, FACS analysis, and others.

Dendritic cells prepared from mice genetically deleted for CD80 and CD86(B7-1 and B7-2) were demonstrated to be less efficient at stimulatingproliferation of CD25⁺ CD4⁺ T cells (FIG. 4), playing a role in of CD25⁺CD4⁺ T suppressor cell expansion. In one embodiment, the dendritic cellsused for the methods of this invention may express, or in anotherembodiment, may be engineered to express a costimulatory molecule. Inone embodiment, dendritic cells used for the methods of this inventionare enriched for CD86^(high) or CD80^(high) expression.

In another embodiment, the dendritic cells used in the methods of thisinvention are selected for their capacity to expand antigen-specificCD25⁺CD4⁺ suppressor cells. In one embodiment, the DCs are isolated fromprogenitors or from blood for this purpose. In another embodiment,dendritic cells expressing high amounts of DEC-205/CD205 are used forthis purpose.

T suppressor cell expansion, in one embodiment, is antigen-specific. Inone embodiment, antigenic peptide or protein is supplied in the culturesimultaneously with dendritic cell contact with CD25⁻ CD4⁺ cells. Inanother embodiment, dendritic cells, which have already processedantigen are contacted with the CD25⁻ CD4⁺ T cells.

In one embodiment, the term “contacting a target cell” refers herein toboth direct and indirect exposure of cell to the indicated item. In oneembodiment, contact of CD25⁻ CD4⁺ cells to an antigenic peptide,protein, cytokine, growth factor, dendritic cell, or combinationthereof, is direct or indirect. In one embodiment, contacting a cell maycomprise direct injection of the cell through any means well known inthe art, such as microinjection. It is also envisaged, in anotherembodiment, that contacting or supplying to the cell is indirect, suchas via provision in a culture medium that surrounds the cell, oradministration to a subject, via any route well known in the art, and asdescribed hereinbelow.

Methods for priming dendritic cells with antigen are well known to oneskilled in the art, and may be effected, as described for example Hsu etal., Nature Med. 2:52-58 (1996); or Steinman et al. Internationalapplication PCT/US93/03141. Antigens may, in one embodiment, be chosenfor a particular application, or, in another embodiment, in accordancewith the methods of this invention, as described further hereinbelow,and may be associated, in other embodiments, with fungal, bacterial,parasitic, viral, tumor, inflammatory, or autoimmune (i.e., selfantigens) diseases.

In one embodiment, antigenic peptide or protein is added to a culture ofdendritic cells prior to contact of the dendritic cells with CD 25⁻ CD4⁺T cells. In one embodiment, soluble peptide or protein antigens are usedat a concentration of between 10 pM to about 10 μM. In one embodiment,30-100 ng ml⁻¹ is used. The dendritic cells are, in one embodiment,cultured in the presence of the antigen for a sufficient time to allowfor uptake and presentation, prior to, or in another embodiment,concurrent with culture with CD25⁻ CD4⁺ T cells. In another embodiment,the antigenic peptide or protein is administered to the subject, and, inanother embodiment, is targeted to the dendritic cell, wherein uptakeoccurs in vivo, for methods as described hereinbelow.

Antigenic protein or peptide uptake and processing, in one embodiment,can occur within 24 hours, or in another embodiment, longer periods oftime may be necessary, such as, for example, up to and including 4 daysor, in another embodiment, shorter periods of time may be necessary,such as, for example, about 1-2 hour periods.

In one embodiment, CD25⁻ CD4⁺ T cell expansion may be stimulated by adendritic cell to T cell ratio of 1:1 to 1:10. In one embodiment, about5 million T cells are administered to a subject.

In another embodiment, the CD25⁺ CD4⁺ T suppressor cells expanded by themethods of this invention are autologous, syngeneic or allogeneic, withrespect to the dendritic cells. In another embodiment, the CD25⁺ CD4⁺ Tsuppressor cells expanded by the methods of this invention are enrichedfor CTLA-4high and/or GITRhigh expression. In another embodiment, theCD25⁺ CD4⁺ T suppressor cells expanded by the dendritic cells in themethods of this invention are engineered to express CTLA-4 and/or GITR.

In another embodiment, the dendritic cells used in the methods of thisinvention are isolated from a subject suffering from an autoimmunedisease or disorder, and in another embodiment, the antigenic peptide orantigenic protein is associated with the autoimmune disease or disorder.The autoimmune disease or disorder may be any of those describedhereinabove, such as for example type I diabetes, and in anotherembodiment, the antigenic peptide or protein may be expressed onpancreatic beta cells. In one embodiment, the antigenic peptide may be aBDC mimetope. In another embodiment, the antigenic peptide or proteinmay be derived insulin, proinsulin, preproinsulin, islet associatedantigen (IAA), glutamic acid decarboxylase (GAD), or islet-specificglucose-6-phosphatase catalytic subunit related protein (IGRP). Asdescribed hereinabove, peptide libraries from these antigens or cellsproducing same may be utilized for any application in this invention.

In another embodiment, the dendritic cells used in the methods of thisinvention are isolated from a subject with an inappropriate orundesirable inflammatory response, and in another embodiment, theantigenic peptide or protein is associated with the inappropriate orundesirable inflammatory response.

In another embodiment, the dendritic cells used in the methods of thisinvention are isolated from a subject with an allergic response, and inanother embodiment, the antigenic peptide or protein is associated withthe allergic response.

In another embodiment, the dendritic cells used in the methods of thisinvention are isolated from a subject who is a recipient of atransplant. In one embodiment, the dendritic cells are isolated from adonor providing a transplant to said subject, and in another embodiment,the antigenic peptide or protein is associated with an immune responsein the subject receiving a transplant from a donor.

In another embodiment, the immune response is a result of graft versushost disease. In another embodiment, the immune response is a result ofhost versus graft disease.

In another embodiment, the dendritic cells are engineered to express anantigen through introduction of a recombinant vector comprising nucleicacid encoding the antigen or encoding a polypeptide sequence comprisingthe antigen. Direct RNA transfection can also be used. Expressionvectors prepared as described above and as generally known by theskilled artisan can be prepared and introduced into dendritic cells toprovide the source of antigen as described herein. Thus, antigencomprising islet beta cell antigen, or antigen from, by way of example,rheumatoid arthritis, multiple sclerosis, myasthenia gravis, perniciousanemia, Addison's disease, lupus erythematosus, Reiter's syndrome,atopic dermatitis, psoriasis or Graves disease, are amenable to suchmethods.

The source of TGF-β1 used in the practice of the embodiments herein maybe provided by any number of sources. In one embodiment, naturallyisolated or recombinant TGF-β1 can be used, such as recombinant humanTGF-β1 purchased from R&D Systems. As shown in the examples herein, theinduction of FoxP3⁺ cells by TGF-β1 was dose dependent, and was evidentin vitro at 0.01 ng/ml and peaked at 1 ng/ml (FIG. 1D). One of skill inthe art will readily determine the necessary amount of TGF-β1 to includein the particular embodiment of the invention being practiced, andadjust the amount accordingly. TGF-β1 can also be provided by includingother TGF-β1-producing cells in the practice of the methods describedherein, such as by including cells engineered to produce TGF-β1, whetherby recombinant means or by induction to produce TGF-β1.

In yet another embodiment, dendritic cells can be engineered to expressTGF-β1 by introducing therein an expression vector encoding TGF-β1. Inanother embodiment, dendritic cells can be induced to produce TGF-β1 orincreased levels of TGF-β1 by, for example, contact with certainmicrobial products or cytokines. In another embodiment, as noted above,an expression vector encoding the desired antigen and in addition anexpression vector encoding TGF-β1 can be introduced into dendritic cellsto provide the requisite components along with the CD25⁻CD4⁺ cells tocarry out the intended methods of the invention. In a furtherembodiment, a single expression vector comprising both antigen andTGF-β1 can be employed.

In one embodiment, the DC expanded CD25⁺ CD4⁺ T cells can be used tosuppress an inflammatory response, in a disease-specific manner. In oneembodiment, the T suppressor cells of this invention may suppress anyautoimmune disease, allergic condition, transplant rejection, or chronicinflammation due to external causes, such as, for example inflammatorybowel disease. It is to be understood that any immune response, whereinit is desired to suppress such a response, the T suppressor cells ofthis invention may be thus utilized, and is an embodiment of thisinvention.

Thus, based on the teaching herein, an isolated, culture-expandedCD25⁺CD4⁺ T suppressor cell population is provided, wherein saidpopulation is prepared by the process of exposing CD25⁻ CD4⁺ T cells todendritic cells, antigen and TGF-β1. The population can further expressFoxp3 on its surface, among other markers. The population can be antigenspecific. In certain embodiments, the dendritic cells exposed to theCD25⁻CD4⁺ T cells are presenting the antigen or a peptide thereof. Asnoted herein above, the antigen is a self-antigen, or a derivativethereof, such as a self antigen is expressed on pancreatic beta cells;alternately a mimetope such as BDC can be used.

In the embodiments in which suppression of a response to a transplantantigen is contemplated, the antigen can be a transplantation antigen.

A method is also provided for producing an isolated, culture-expandedCD25⁺CD4⁺ T suppressor cell population, comprising the steps of

a. contacting a population of CD25⁻ CD4⁺ T cells with dendritic cells;an antigen selected from the group consisting of an antigenic peptide,an antigenic protein, and a derivative thereof; and TGF-β1, for a periodof time resulting in antigen-specific CD25⁺ CD4⁺ T cell differentiationand expansion; and

b. isolating the expanded CD25⁺ CD4⁺ T cells obtained in (a).

In the foregoing method, the CD25⁺CD4⁺ T suppressor cell populationresulting from the methods herein can further express Foxp3 on itssurface. The CD25⁺CD4⁺ T suppressor cell population can be antigenspecific. The dendritic cells can present the antigen or a peptidethereof, and the antigen can be a self-antigen, or a derivative thereof.In one merely exemplary embodiment, the self antigen is expressed onpancreatic beta cells. In other embodiments, the antigen is atransplantation antigen. As noted above, the source of antigen, andindependently, of TGF-β1, can be the dendritic cells, or other celltypes, for this and other embodiments of the invention.

A method is provided for delaying the onset, reducing incidence,suppressing or treating autoimmunity, an autoimmune disease or anautoimmune disorder in a subject, comprising the steps of:

-   -   a. contacting a population of CD25⁻ CD4⁺ T cells with dendritic        cells; an antigen selected from the group consisting of an        antigenic peptide, an antigenic protein, and a derivative        thereof; and TGF-β1, for a period of time resulting in        antigen-specific CD25⁺ CD4⁺ T cell differentiation and        expansion; and    -   b. administering the expanded CD25⁺ CD4⁺ T cells obtained in (a)        to a subject.

In the practice of the aforementioned method, the autoimmune responsecan be directed towards rheumatoid arthritis or diabetes. In otherembodiments, the method can be used to suppress an inflammatoryresponse, or suppress an allergic response. In other embodiments it canbe used to downmodulate an immune response. Non-limiting examples ofsuch immune responses include graft versus host disease and host versusgraft disease.

Similarly, a method is provided for downmodulating an immune response ina subject, comprising the steps of:

-   -   a. contacting a population of CD25⁻ CD4⁺ T cells with dendritic        cells; an antigen selected from the group consisting of an        antigenic peptide, an antigenic protein, and a derivative        thereof; and TGF-β1, for a period of time resulting in        antigen-specific CD25⁺ CD4⁺ T cell differentiation and        expansion; and    -   b. administering the expanded CD25⁺ CD4⁺ T cells obtained in (a)        to a subject.

In one embodiment, cells for administration to a subject in thisinvention may be provided in a composition. These compositions may, inone embodiment, be administered parenterally or intravenously. Thecompositions for administration may be, in one embodiment, sterilesolutions, or in other embodiments, aqueous or non-aqueous, suspensionsor emulsions. In one embodiment, the compositions may comprise propyleneglycol, polyethylene glycol, injectable organic esters, for exampleethyl oleate, or cyclodextrins. In another embodiment, compositions mayalso comprise wetting, emulsifying and/or dispersing agents. In anotherembodiment, the compositions may also comprise sterile water or anyother sterile injectable medium. In another embodiment, the compositionsmay comprise adjuvants, which are well known to a person skilled in theart (for example, vitamin C, antioxidant agents, etc.) for some of themethods as described herein, wherein stimulation of an immune responseis desired, as described further hereinbelow.

In one embodiment, the cells or compositions of this invention may beadministered to a subject via injection. In one embodiment, injectionmay be via any means known in the art, and may include, for example,intra-lymphoidal, or subcutaneous injection.

In another embodiment, the T suppressor cells and dendritic cells foradministration in this invention may express adhesion molecules fortargeting to particular sites. In one embodiment, T suppressor celland/or dendritic cells may be engineered to express desired molecules,or, in another embodiment, may be stimulated to express the same. In oneembodiment, the DC cells for administration in this invention mayfurther express chemokine receptors, in addition to adhesion molecules,and in another embodiment, expression of the same may serve to attractthe DC to secondary lymphoid organs for priming. In another embodiment,targeting of DCs to these sites may be accomplished via injecting theDCs directly to secondary lymphoid organs through intralymphatic orintranodal injection.

In one embodiment, the antigen is delivered to dendritic cells in vivoin the steady state, which, in another embodiment, leads to expansion ofdisease specific suppressors. Antigen delivery in the steady state canbe accomplished, in one embodiment, as described (Bonifaz, et al. (2002)Journal of Experimental Medicine 196: 1627-1638; Manavalan et al. (2003)Transpl Immunol. 11: 245-58).

In one embodiment, the antigens are targeted to dendritic cells in vivoto modulate suppressor cells as described herein. In one embodiment,antigens are targeted to subsets of dendritic cells, which expandsuppressors in vivo. In one embodiment, the antigen may be geneticallyengineered, for example, and in another embodiment, an islet cellautoantigen is engineered to be expressed as a fusion protein, with anantibody that targets dendritic cells, such as, for example, the DEC-205antibody. Methods for accomplishing this are known in the art, and maybe, for example, as described, Hawiger D. et al. J. Exp. Med., Volume194, (2001) 769-780.

In another embodiment, select types of dendritic cells in vivo functionto expand the T suppressor cells. In one embodiment, the use ofdendritic cells and a single antigen, will block a disease, which iscaused by an autoimmune response directed to multiple antigens.

In one embodiment, the suppressor T cells of this invention may beadministered to a recipient contemporaneously with a graft ortransplant. In another embodiment, the suppressor T cells of thisinvention may be administered prior to the administration of thetransplant. In one embodiment, the suppressor T cells of this inventionmay be administered to the recipient about 3 to 7 days beforetransplantation of the donor tissue. The dosage of the suppressor Tcells varies within wide limits and will, of course be fitted to theindividual requirements in each particular case, and may be, in anotherembodiment, a reflection of the weight and condition of the recipient,the number of or frequency of administrations, and other variables knownto those of skill in the art. The suppressor T cells can beadministered, in other embodiments, by a route, which is suitable forthe tissue, organ or cells to be transplanted. The T suppressor cells ofthis invention may be administered systemically, i.e., parenterally, byintravenous injection or targeted to a particular tissue or organ, suchas bone marrow. The suppressor T cells of this invention may, in anotherembodiment, be administered via a subcutaneous implantation of cells orby injection of stem cell into connective tissue, for example muscle.

In one embodiment, the term “downmodulating” refers to inhibition,suppression or prevention of a particular immune response. In oneembodiment, downmodulating results in diminished cytokine expression,which provides for diminished immune responses, or their prevention. Inanother embodiment, downmodulation results in the production of specificcytokines which have a suppressive activity on immune responses, or, inanother embodiment, inflammatory responses in particular.

The following non-limiting examples may help to illustrate someembodiments of the invention.

EXAMPLES Materials and Methods

Mice. NOD, NOD.scid, and BDC2.5 TCR transgenic mice were purchased fromThe Jackson Laboratory (West Grove, Pa.). Mice were used according toinstitutional guidelines and protocols approved by the institutionalAnimal Care and Use Committees at Northwestern University, CornellUniversity, and The Rockefeller University.

Antibodies. Biotinylated mAbs for CD8 (53-6.7), CD25 (7D4), Ly-76(Ter-119), Grl (RB6-8C5), CD49b/Pan-NK (DX5), B220 (RA3-682), and CD11b(M1/70); FITC-conjugated anti-CD4 (GK1.5), CD11c (HL3), I-A^(g7) (OX-6);PE-conjugated anti-IL-17 (TC11-18H10), IL-10 (JES5-16E3), CD25 (PC61),CD86 (GL1), GITR (DTA-1); and APC-conjugated anti-CD62L (MEL-14) werefrom BD Biosciences (Franklin Lakes, N.J.). PE-conjugated anti-CD152(UC10-4B9) and Foxp3 (FJK-16s) in addition to APC-conjugated anti-CD25(PC61) were from eBioscience (San Diego, Calif.). A hybridoma expressingthe anti-clonotype antibody that is specific for BDC2.5 TCR (BDC) wasprovided by O. Kanagawa (Washington University, St. Louis, Mo.), and theantibody was purified and biotinylated. Recombinant human TGF-β1 wasobtained from R&D Systems, (Minneapolis, Minn.).

Cell Purifications. Splenic DCs were isolated from NOD males asdescribed in ref. 36. In brief, spleens from normoglycemic NOD malesbetween the ages of 4 and 10 weeks were first digested with collagenaseD (Sigma-Aldrich, St. Louis, Mo.) followed by the enrichment of the DCfraction with 30% BSA density gradient. The CD11c fraction was thenpurified with magnetic microbeads (Miltenyi Biotec, Auburn, Calif.). Thepurity of DCs was routinely >90%. DCs were irradiated with 15 Gy beforetheir use as APCs. Naïve CD4⁺CD25⁻ cells were purified from BDC2.5spleen and lymph nodes. Cells were first enriched by depletion(anti-CD8, CD25, Ter119, Grl, DX5, B220, CD11b) followed by FACS sortingfor the CD4⁺CD25⁻CD62L⁺ population to >95% purity.

Cell Culture, Proliferation Assays, and Cytokine Detection. The sequenceof the mimetope peptide used (BDC) was RVRPLWVRME (SEQ ID NO: 4.) Atotal of 2×10⁴ per well of CD4⁺ CD25⁻ BDC2.5 T cells were cultured for6-10 days with splenic DCs at a 3:1 T/DC cell ratio in 96-well plateswith 100 ng/ml BDC peptide, either with or without TGF-β1 at indicatedconcentrations. Alternatively, T cells were cultured with 10 μg/mlanti-CD3 (a gift from Terrence Barrett, San Jose, Calif.) and 2 μg/mlanti-CD28 (BD Biosciences, San Jose, Calif.) for 6 days. For functionaltests, DCs were removed by CD11c antibody-conjugated magneticmicrobeads, and CD25⁺ cells were further enriched by labeling them withPE-conjugated anti-CD25 (PC61) and anti-PE microbeads. For proliferationassays, freshly isolated CD4⁺CD25⁻ BDC2.5 T cells were cultured with NODwhole spleen cells at a T/APC cell ratio of 1:5 and 100 ng/ml BDCpeptide. [³H]thymidine (1 μCi per well; PerkinElmer, San Jose, Calif.)was added for the last 18 h of a 72-h assay. For suppression assays, thecultured CD25⁺T cells were added to proliferation assays at theindicated ratios and [³H]thymidine uptake was measured. For cytokineassays, culture supernatants were tested with the LiquiChip Mouse10-cytokine assay kit (Qiagen, Valencia, Calif.). For intracellularcytokine detection, cells were first stimulated with leukocyteactivation mixture (BD Biosciences) for 4 h before being stained inaccordance with the manufacturer's protocol.

Real-Time PCR. Total RNA was extracted with the RNeasy mini kit(Qiagen). The sequences of primers and probe for mouse Foxp3 were asfollows: sense 5′-AGGAGAAGCTGGGAGCTATGC-3′ (SEQ ID NO: 1); anti-sense5′-TGGCTACGATGCAGCAA GAG-3′ (SEQ ID NO:2); probe 5′-FAMAGCGCCATCTTCCCAGCCAGG TAMRA-3′ (SEQ ID NO:3). The final quantity of mRNAwas calculated as copies per microgram of RNA and standardized accordingto 18s RNA.

Diabetes Experiments. For NOD.scid experiment, diabetes was induced in5- to 9-week-old NOD.scid mice with an i.v. injection of 10⁷ spleencells from female NOD mice with diabetes. Indicated numbers of theinduced CD4⁺CD25⁺ T cells were coinjected where indicated. Urine glucosewas checked two to three times per week, and the development of diabetesin NOD.scid mice was defined as three consecutive positive urine glucosereadings.

The spontaneous development of diabetes in female NOD mice was definedas two consecutive blood glucose levels of >250 mg/dl. Islet isolationand transplantation were performed as described in ref. 22. In brief,islets were handpicked to a purity of >80% for transplant, and 500-600islets were transplanted into the kidney subcapsular space of newlydiabetic NOD female mice. For cell and islet cotransplants, theindicated numbers of T cells were mixed with islets immediately beforetransplantation. Graft destruction was diagnosed by the recurrence ofhyperglycemia (blood glucose level >250 mg/dl on two consecutivereadings).

Statistical Analysis. For analysis of real-time PCR data, we used theStudent's t test. To analyze the incidence of diabetes in NOD.scid andsyngeneic islet graft survival in NOD recipients, we used analysis ofvariance. P<0.05 was considered to be significant.

Example 1 Splenic CD11c⁺ DCs Induce Differentiation of CD4⁺CD25⁺Foxp3⁺ TRegs from CD4⁺CD25⁻ T Cells in the Presence of TGF-β1.

To test the role of DCs in the de novo differentiation ofCD4⁺CD25⁺Foxp3⁺ T regs, CD4⁺CD25⁻ T cells were used from the BDC2.5 TCRtransgenic NOD mice. These T cells respond to both an unidentifiedautoantigen expressed in the secretory granules of islet βcells and amimetope peptide (BDC). CD11c⁺ DCs were isolated from splenocytes of NODmice and characterized for expression of CD40, CD86, and MHCII (FIG.1A). Compared with LPS-matured DCs, these freshly isolated DCs expressweaker CD40 and MHC II and significantly less CD86 (data not shown),suggesting a relatively immature phenotype. A starting population ofCD4⁺CD25⁻CD62L⁺ BDC2.5 T cells was also characterized, after FACSsorting to a purity of >95%, and found the expected small fraction ofFoxp3⁺ cells (FIG. 1B). DCs were then added together with the BDCpeptide to the CD4⁺CD25⁻ BDC2.5 T cells in the presence or absence ofTGF-01. After 6 days of culture, good induction of Foxp3 mRNA (FIG. 1D)and protein (FIG. 1B) were observed, but only when TGF-β1 was includedin the cultures. In the presence of TGF-β1, the frequency of Foxp3⁺cells increased to 88.3±7% (n=3; FIG. 1B), and their numbers increased≈50- to 100-fold (FIG. 1C). The newly formed Foxp3⁺ cells appeared by 2days of culture, and the total number of Foxp3⁺ cells peaked at 4 daysand decreased after 6 days. Because of the rapid appearance of theFoxp3⁺ cells, the increase observed is unlikely to be caused by theexpansion of the few Foxp3⁺ cells in the starting population. In theabsence of TGF-β1, the percentage of Foxp3⁺ cells remained close tobaseline, although CD25 expression was still induced (FIG. 1B).Quantification of Foxp3 mRNA expression by real-time RT-PCR demonstratedthat the level induced by the DCs and TGF-β1 was equivalent to thatfound in naturally occurring T regs (FIG. 1D). The induction of Foxp3⁺cells by TGF-1 was dose-dependent, being readily evident at 0.01 ng/mland peaking at 1 ng/ml (FIG. 1E). Therefore, DCs can serve as effectiveAPCs for differentiating Foxp3⁺ T cells from CD4⁺CD25⁻Foxp3⁻ precursorsin the presence of low-dose TGF-β1.

Example 2 Characterization of CD4⁺CD25⁺Foxp3⁺ T Regs Induced by DCs andTGF-β1

Cytokine expression by T cells cultured with splenic DCs and TGF-1 wasdetermined. No IFN-γ or IL-10 was observed (FIG. 2A). Because TGF-β1 isable to induce IL-17-secreting cells or Foxp3⁺ cells depending on thepresence or absence of IL-6, IL-17 production was also tested. T cellscultured with splenic DCs and TGF-β1 were negative for IL-17 expression,whereas as a positive control, T cells cultured with IL-6 and TGF-β1 didexpress IL-17 (FIG. 2A).

Next, expression was measured of proteins associated with T reg functionin the CD4⁺CD25⁺Foxp3⁺ T cells differentiated by splenic DCs and TGF-β1.As shown in FIG. 2B, a greater percentage of T cells cultured in thepresence of TGF-β1 retained CD62L expression compared with thosecultured in the absence of TGF-β1. T cells cultured either with orwithout TGF-β1 up-regulated both CTLA-4 and glucocorticoid-induced TNFreceptor (GITR; FIG. 2B), whereas freshly purified T cells were negativefor both (data not shown).

Because the level of TCR expression contributes to the avidity of T cellresponses, BDC clonotype expression was measured before and afterstimulation. Approximately 90% of freshly isolated CD4⁺ BDC2.5 T cellswere clonotype⁺ (FIG. 2C). Stimulation with splenic DCs pulsed with theBDC peptide maintained high levels of clonotype expression. In contrast,nonspecific stimulation with anti-CD3/CD28 resulted in much lowerclonotype expression (FIG. 2C). These observations indicate that the DCand TGF-β1-induced T regs share many features with natural T regs.

Example 3 In Vitro Suppression of CD4⁺CD25⁺Foxp3⁺ T Regs Induced by DCsand TGF-β1

To test for the suppressive function of the CD4⁺CD25⁺Foxp3⁺ T cellsinduced with splenic DCs and TGF-β1, an in vitro assay was used first.CD11c⁺ cells were depleted and CD25⁺ T cell fraction enriched from 6-daycultures with DCs and the resulting CD4⁺CD25⁺ T cells added in gradeddoses to responder CD4⁺CD25⁻ BDC2.5 T cells. Inhibition of proliferationwas measured to BDC peptide presented by whole NOD splenic APCs. Asshown in FIG. 3A, in the presence of TGF-β1, the DC-induced CD4⁺CD25⁺ Tcells were 91% Foxp3⁺ after enrichment. They were anergic in response toBDC peptide and were able to block the proliferation of naïve BDC2.5 Tcells to BDC peptide (70% suppression at a 1:1 ratio). This ratio of Tregs needed for suppression was greater than required for DC-expandednatural T regs, which gave similar suppression of proliferation with4-fold fewer T regs. Suppression of IFN-γ secretion was also observedand at a responder/suppressor ratio as low as 8:1 (FIG. 3A). Incontrast, in the absence of TGF-β1, the resulting CD4⁺CD25⁺ T cells wereonly 11% Foxp3⁺ after enrichment. They showed vigorous proliferation toBDC peptide themselves, were unable to suppress proliferation of naïveBDC2.5 T cells, and led to augmented IFN-γ secretion (FIG. 3B).Therefore, the induced Foxp3⁺ T regs have some suppressive function invitro, although they are less potent than natural T regs after expansionwith DCs.

Example 4 CD4⁺CD25⁺Foxp3⁺ T Regs Induced by DCs and TGF-β1 SuppressAutoimmune Diabetes in Vivo

A more critical function for naturally occurring CD4⁺CD25⁺ T regs is thesuppression of autoimmunity in vivo. To test whether the T regs inducedby splenic DCs and TGF-β1 could inhibit autoimmune diabetes, adoptivetransfer was first used in NOD.scid recipients. In this model, injectionof diabetogenic splenocytes from acutely diabetic NOD mice into NOD.scidrecipients results in rapid autoimmune destruction of the nativepancreas and consequent development of hyperglycemia. Because a knownquantity of diabetogenic splenocytes is injected into the NOD.scidrecipients, this model allows for a measurement of the potency of theDC-induced T regs according to the kinetics of diabetes developmentafter injection. As shown in FIG. 4, i.v. coinjection of 3×10⁵ of theDC+ TGF-β1-induced CD4⁺CD25⁺ T cells along with 10⁷ diabetogenicsplenocytes resulted in complete protection from the development ofdiabetes (0/6 recipients developed diabetes at 120 days afterinjection). In addition, 10-fold fewer (3×10⁴) of the same T cellscoinjected with 10⁷ diabetogenic splenocytes still resulted in asignificant delay of onset and a lower incidence of diabetes. Incontrast, injection of either dose of the CD4⁺CD25⁺ T cells fromcultures without TGF-β1 along with 10⁷ diabetogenic splenocytes resultedin accelerated onset of diabetes in NOD.scid recipients.

Next, the efficacy of these T regs was tested in blocking autoimmunedestruction of a syngeneic islet graft in spontaneously diabetic NODrecipients. This model represents a clinically relevant scenario ofdiabetes pathogenesis in which islet-specific effector cells are alreadypresent in a nonlymphopoenic host. Without intervention, ongoingautoimmunity directed toward the transplanted islet β cells results ingraft destruction within 5-17 days after transplantation. To avoid theconfounding factor of T reg cell trafficking, the T regs were directlydeposited at the site of the islet graft, i.e., the kidney subcapsularspace. When 3×10⁵ DC+ TGF-β1-induced CD4⁺CD25⁺ T cells along with thesyngeneic islets were cotransplanted into the kidney subcapsular spaceof diabetic NOD recipients, there was a significant prolongation ofgraft survival (FIG. 5). In contrast, CD4⁺CD25⁺ T cells induced in theabsence of TGF-β1-accelerated isograft destruction.

Thus, in both the adoptive transfer NOD.scid model and the spontaneousdiabetes NOD model, the CD4⁺CD25⁺Foxp3⁺ T regs induced by DCs and TGF-β1were able to effectively block autoimmunity mediated by a diverserepertoire of autoreactive TCR specificities, analogous to thepreviously reported properties of “natural” T regs.

What is claimed is:
 1. A method for producing an isolated, antigen specific culture-expanded CD25⁺CD4⁺ T suppressor cell population, comprising: a) purifying a population of CD25⁻CD4⁺ T cells; b) purifying a greater than 90% population of immature dendritic cells; c) contacting the population of CD25⁻CD4⁺ T cells with the immature dendritic cells; an antigen selected from the group consisting of an antigenic peptide or an antigenic protein; and TGF- β1, for a period of time resulting in antigen-specific CD25⁺CD4⁺ T cell differentiation and expansion, wherein the ratio of the immature dendritic cells to the CD25⁻CD4⁺ T cells is between 1:1 and 1:10 and the concentration of the antigen is 30-100 ng/ml; and d) isolating the expanded CD25⁺CD4⁺ T cells obtained in (c), thereby producing an isolated, antigen specific culture-expanded CD25⁺CD4⁺ T suppressor cell population with an in vivo immune suppressive activity, wherein the CD25⁺CD4⁺ T suppressor cell population do not express IL-10.
 2. The method of claim 1, wherein said isolated, antigen specific culture-expanded CD25⁺CD25⁺ T suppressor cell population further expresses Foxp3.
 3. The method of claim 1, wherein the dendritic cells are presenting the antigen or a peptide thereof, or are engineered to express the antigen or a peptide thereof.
 4. The method of claim 1, wherein the antigen is a pancreatic beta cell antigen, a transplantation antigen, or a rheumatoid arthritis antigen.
 5. The method of claim 1, wherein said population suppresses or down modulates an inflammatory response, an allergic response, or an immune response.
 6. The method of claim 5, wherein said immune response is graft versus host disease or host versus graft disease.
 7. The method of claim 1, wherein the TGF- β1 is exogenous or expressed by the dendritic cells or other cells.
 8. The method of claim 1, wherein said dendritic cells are isolated from a subject suffering from an autoimmune disease or disorder.
 9. The method of claim 8, wherein said antigenic peptide or antigenic protein is associated with said autoimmune disease or disorder.
 10. The method of claim 9, wherein said autoimmune disease or disorder is type I diabetes, graft-vs.-host disease or host-vs.-graft disease.
 11. The method of claim 9, wherein said antigenic peptide or protein is expressed in pancreatic beta cells.
 12. The method of claim 11 wherein said antigenic peptide is a BDC mimetope.
 13. The method of claim 2, wherein said dendritic cells are isolated from a subject with an allergic response, a recipient of a transplant, or a donor providing a transplant to said subject. 